package com.emzoism.springboot.springbootdive.util;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

/**
 * Spring的ApplicationContext的持有者,可以用静态方法的方式获取spring容器中的bean
 * @Component不能去掉，否则无法调用setApplicationContext方法
 * 程序启动的时候，会自动将ApplicationContext进行注入
 */
//@Component
public class SpringContextUtil implements ApplicationContextAware {
	/**
	 * 上下文对象实例
	 */
	private static ApplicationContext applicationContext;
 
	@Override
	@Autowired
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		SpringContextUtil.applicationContext = applicationContext;
	}
	/**
	 * 获取application上下文对象
	 * @return
	 */
	public static ApplicationContext getApplicationContext() {
		assertApplicationContext();
		return applicationContext;
	}
 
	/**
	 * 通过name获取bean
	 * @param beanName
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public static <T> T getBean(String beanName) {
		assertApplicationContext();
		return (T) applicationContext.getBean(beanName);
	}
 
	/**
	 * 通过class获取bean
	 * @param requiredType
	 * @return
	 */
	public static <T> T getBean(Class<T> requiredType) {
		assertApplicationContext();
		return applicationContext.getBean(requiredType);
	}
 
	private static void assertApplicationContext() {
		if (SpringContextUtil.applicationContext == null) {
			throw new RuntimeException("applicaitonContext属性为null,请检查是否注入了SpringContextHolder!");
		}
	}
 
}